The invention relates to a method, article and system for monitoring a combustion system with a selected binder. More particularly, the invention is directed to an indicator in a selected binder.
A gas turbine engine includes in serial flow communication, one or more compressors followed in turn by combustors and high and low pressure turbines disposed about a longitudinal axial centerline within an annular outer casing. During operation, the compressors are driven by the turbine to compress air, which is mixed with fuel and ignited in the combustors to generate hot combustion gases. The combustion gases flow downstream through the high and low pressure turbines to extract energy to drive the compressors to produce output power either as shaft power or thrust.
The operating environment within a gas turbine engine is both thermally and chemically hostile and deleterious to certain engine components. If the components are located in certain sections of the engine such as the combustors, high pressure turbine or augmentor, they cannot withstand long service exposure. Typically the surfaces of these components are coated with a protective system, such as a thermal barrier coating system. A thermal barrier coating system includes an environmentally-resistant bond coating and a thermal barrier coating (TBC) of a ceramic material applied as a topcoat over a bond coat. Bond coats are typically formed of an oxidation-resistant alloy such as MCrAlY where M is iron, cobalt and/or nickel, or a diffusion aluminide or platinum aluminide. At high temperature, these bond coats form an oxide layer or scale that chemically bonds the ceramic layer to the underlying component.
Maximum power output of a gas turbine is achieved by heating the gas flowing through the combustion section to as high a temperature as is feasible. However, the heated gas also heats the various turbine components as it flows through the turbine. These components may be critical components that have a direct impact on the operation and efficiency of the turbine. With time, continued flow of excessively high temperature air wears down the component protective TBC layer.
Additionally, unnecessarily high turbine engine combustion temperatures can compromise fuel efficiency and increase emission pollution. For example, in a gas turbine designed to emit nine nitrogen oxide (NOx) particles per million (ppm), an increase from 2730° F. (1499° C.) to 2740° F. (1504° C.) reduces turbine efficiency by about two percent and increases NOx emissions by about two ppm. On an annual basis, this can amount to millions of dollars of lost revenue and to several tons increase in NOx emission.
So called “smart materials” have been proposed to monitor and detect on-line wear due to high temperature operation and other effects of operation in a corrosive environment. A smart material senses a change in an environment, and then using a feedback system, makes a useful response. Hanneman, U.S. Pat. No. 4,327,155 and Siemers et al., U.S. Pat. No. 4,327,120 provide examples of smart materials. Hanneman teaches a substrate that has a protective metallic or ceramic coating. The substrate is subject to a high degree of surface erosion that eventually wears away the protective coating. The protective coating can be periodically renewed or replaced by plasma or flame spraying with a powdered metal or a powdered metal oxide blend. Hanneman proposes a smart coating that includes a UV sensitive phosphor. The UV sensitive material-containing coating emits UV sensitive material as it wears. Monitoring the emission of UV sensitive material can indicate when additional plasma or flame spraying of the metal substrate with powdered metal or powdered metal oxide should be undertaken. Siemers et al. teaches that the particulate size of the phosphor component of the UV sensitive indicating material should be sized according to an Energy of Melting formula.
The Hanneman and Siemers et al. materials can be used in systems to estimate parts life. Typically, life monitoring takes the form of detecting UV sensitive material and relating a quantity of detected material over a period of time to a data base that includes relationships of material over time with coating wear. However, detected material over time and wear relationship data is not available for new systems or, for that matter, for most old systems. Additionally, oftentimes known indicators are applied to a component in a non-uniform manner. In this case, detected indicators do not accurately reflect wear or other operational effects.
Some coating life monitoring methods are based on average effects of stress and temperature profiles of all the parts. These methods are unable to focus on individual parts because they do not take into account the exposure circumstances of a particular part or section of a part. A particular part or section of a part may uniquely encounter wear or damage caused by foreign objects, varying operating conditions from site to site and occasional turbine over-firing. Such circumstances can uniquely influence coating and part life.
Hence, it is desirable to monitor a particular part that may be subjected to a local heating that is not represented by an overall system temperature. There is a need for a method, article and system to sense and monitor UV sensitive material emission from a coating to provide accurate information and particular location information to determine wear, maintenance scheduling and to reduce noxious emissions.